The study, compiled by Harvard University PhD student Laura Trucco, analysed worldwide searches for "iPhone slow" and found that the search term spikes massively around the time of new phone releases, The Times reports.

The study compared those results with similar searches for one of Apple's main rivals but found that the term "Samsung Galaxy slow" was unaffected by new releases from Samsung.

Writing for the New York Times, Sendhil Mullainathan, a professor of economics at Harvard, said that the results were "striking".

"Wouldn't many business owners love to make their old product less useful whenever they released a newer one?" Mullainathan wrote. "When you sell the device and control the operating system, that's an option".

On the other hand, conspiracy theorists might also see an economic reason for Google to hide search results displaying peaks of concern about the speed of Android operating systems built by Google and used in Samsung smartphones.

Mullainathan notes that the research does not prove that Apple has done anything wrong. "No matter how suggestive," he says, "this data alone doesn't allow you to determine conclusively whether my phone is actually slower and, if so, why."

He said that there are other plausible explanations for why an older model iPhone may slow down. The latest version of the Apple operating system, iOS, is always tailored to the newest device and may therefore not work as efficiently on older models.

Also, artificially slowing phones comes with many problems: "First, the legal risk," Mullainathan says. "Second, competition and consumer rationality should combine to thwart this strategy. All a competitor needs to do is to offer a smartphone that doesn't become a brick as quickly, and more people should buy it."